1. Field of the Invention
This invention relates to multi-speed systems integrated into bicycles for enhancing propulsion performance.
2. Description of the Related Art
A great multitude of bicycles manufacturers produce bikes having multi-speed systems that allow a rider to change gears to increase speed and decrease pedaling effort when experiencing pedaling resistance. These multi-speed systems are ergonomically accessible to the rider and very convenient.
The standard or most common multi-speed systems used on bicycles are mechanical configurations that allow the rider to manually derail the chain from one sprocket so that it may catch on and completely engage another. Although these systems have improved over time, because of their mechanical nature they present various problems to the rider.
Bicycles with derailleur systems have the potential to skip gears when being manually shifted from one gear to the intended gear. They also have the potential to acquire resistance to shifting from one sprocket to another sprocket, resulting in stiff gear changing levers or handles.
Front derailleur systems have the potential possibility to cause damage to the rider's clothing. Since the crank sprockets must be between the wheels of conventional bicycles so that the rider's feet may rotate them, this close proximity of the crank sprocket to the rider's feet leaves the rider's lower pant edge or a woman's dress edge open to being snatched in between the chain and crank sprocket. Such scenarios may result in the rider's clothes being torn or irremovable oil stains smeared on the riders clothing. Other problems related to derailleur systems include the following:
(a) chain derailing that is not smooth;
(b) a chain removed from a sprocket that does not catch on to another sprocket, resulting in the unlinking of transmission power to the rear wheel; and
(c) the chain skipping sprocket teeth while pedaling.
An example of such a derailleur system can be illustrated in U.S. Patent application Pub. No. US 2006/0194660 by Satoshi Shahana. Other multi-speed systems use lever machines exploiting the mechanical advantages of the lever by locating the transmission drive mechanism close to the fulcrum, while the applied force to the load is farther away from the fulcrum. An example of a lever powered bicycle is illustrated in (U.S. Pat. No. 4,666,173 to Garnard E. Graham. The invention has multiple mechanical configurations for a multi-speed system applied to the lever powered bicycle. Besides having the problems related to derailleur systems as stated before, this invention using a derailleur (FIG. 5) to change the sprocket ratio to increase speed or decrease effort, does not have a clear manually controlled means for changing the chain from one sprocket to the other. According to FIG. 1 (U.S. Pat. No. 4,666,173) there is the disadvantage of not being able to increase rear wheel revolutions per pedal. For example, if the bike increased in speed due to gravity pull on the bike while moving downhill, the rider would have to pedal faster when the bracket is farthest away from the fulcrum in order to increase the speed of the bike. The Lever Enhanced Pedaling System (LEPS) with multi-speed system can provide more revolutions per pedal when the carriage is farthest away from the fulcrum and add more torque to speed without changing the pedaling range or increasing the pedaling rate to keep up with the increase in wheel revolutions. In FIG. 6 (U.S. Pat. No. 4,666,173) wheel revolutions per pedal is increased as the linear chain connected to the bracket is moved farther away from the fulcrum, but this lacks more range than a curved linear transmission means provided by the LEPS with multi-speed system. This is because the circumference of a curve has more surface length than a straight line.
In U.S. Pat. No. 5,988,662 awarded to John Staehlin, the invention has its multi-speed changing mechanism integrated into its pedal assembly. Although this apparatus has similarities to the LEPS, there is no clear mechanical means of moving both propulsion loads or slide blocks (52) closer or away from the fulcrum simultaneously with precision. The LEPS has manual handles on opposite sides of the frame close to the handle bars, which would allow the rider to pull up the multi-speed handle in order to move the propulsion loads or carriages of both lever machines closer to the fulcrum simultaneously, with slip lock motion in that direction and vice versa, in the in the opposite direction, when the multi-speed handle is pulled downwards. Furthermore, the “L” shaped lever offers more mechanical advantage than curved shaped lever of this apparatus because its length is beyond the axle of the rear wheel, thus spreading pedaling effort along a longer distance.
In U.S. Pat. No. 5,335,927 awarded to Islas, the multi-speed system in FIG. 2 has duplicate anchors with the ability to be moved within separate slots having upper rounded notches to hold the anchor in place. The anchor pulls the chain when the pedal is depressed. However, there is no clear means to manually change the anchor from one notch to another while a rider is pedaling the bike. Ergonomically, the multi-speed system of the LEPS has a manual speed changing apparatus close in proximity to the rider's hands. Furthermore, the slot FIG. 2 (U.S. Pat. No. 5,335,927) where change in mechanical advantage is to occur is further away from the fulcrum in distance relative to the area of applied force or pedals. Thus, the advantages of this lever machine are not being fully exploited, because the mechanisms that changes wheel revolutions per pedal are not positioned close to the fulcrums.